On 13-12-21, 13:46, Bard Liao wrote:
From: Ranjani Sridharan ranjani.sridharan@linux.intel.com
This patch provides both a simplification of the suspend flows and a better balanced operation during suspend/resume transition, as part of the transition of Sound Open Firmware (SOF) to dynamic pipelines: the DSP resources are only enabled when required instead of enabled on startup.
The exiting code relies on a convoluted way of dealing with suspend signals. Since there is no .suspend DAI callback, we used the component .suspend and marked all the component DAI dmas as 'suspended'. The information was used in the .prepare stage to differentiate resume operations from xrun handling, and only reinitialize SHIM registers and DMA in the former case.
While this solution has been working reliably for about 2 years, there is a much better solution consisting in trapping the TRIGGER_SUSPEND in the .trigger DAI ops. The DMA is still marked in the same way for the .prepare op to run, but in addition the callbacks sent to DSP firmware are now balanced.
Normal operation: hw_params -> intel_params_stream hw_free -> intel_free_stream
suspend -> intel_free_stream prepare -> intel_params_stream
This balanced operation was not required with existing SOF firmware relying on static pipelines instantiated at every boot. With the on-going transition to dynamic pipelines, it's however a requirement to keep the use count for the DAI widget balanced across all transitions.
The component suspend is not removed but instead modified to deal with a corner case: when a substream is PAUSED, the ALSA core does not throw the TRIGGER_SUSPEND. This is problematic since the refcount for all pipelines and widgets is not balanced, leading to issues on resume. The trigger callback keeps track of the 'paused' state with a new flag, which is tested during the component suspend called later to release the remaining DSP resources. These resources will be re-enabled in the .prepare step.
The IPC used in the TRIGGER_SUSPEND to release DSP resources is not a problem since the BE dailink is already marked as non-atomic.
Acked-By: Vinod Koul vkoul@kernel.org